Martine Leermakers

Accumulation of trace metals in the muscle and liver tissues of five fish species from the Persian Gulf

In this study, concentrations of 16 elements were quantified in muscles and livers of 141 fishes belonging to five commercially species. It was also our intention to evaluate potential risks to human health associated with seafood consumption. The grunt, flathead, greasy grouper, tiger-tooth croaker and silver pomfret fish species were obtained from Abadan, Deylam, Bushehr-Nirogah, Dayyer port, Lengeh port and Abbas port in Hormozgan, Bushehr and Khozesran provinces at the Iranian waters of the Persian Gulf. The contents of Al, As, Be, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni, Sb, Tl, V and Zn in fish muscles and livers were determined by Inductively Coupled Plasma Mass Spectrometry (ICP MS), after digestion in a CEM (Mars 5) microwave oven using nitric acid and hydrogen peroxide. Our results indicated that almost all metals were more accumulated in younger flathead, greasy grouper and tiger-tooth fishes. Contrary to the other fish species, grunt seems to stronger accumulating elements in the older fishes. Strong and positive correlations were observed in three or more of the fish species between V, Al, Fe, Tl, Co and Pb. The results confirmed that fish muscle and liver tissues appeared to be good bio-indicators for identification of coastal areas exposed to metallic contaminants. The results also showed that the element levels in the muscles of all fishes in our study were lower than the maximum allowable concentrations and pose no threat to public health, except for arsenic.

Mercury in the Southern North Sea and Scheldt estuary

Abstract Dissolved and particulate mercury and methylmercury concentrations were determined in the Southern Bight of the North Sea and the Scheldt estuary in the period 1991–1999. Mercury and methylmercury concentrations are higher before 1995 than after 1995, especially in the fluvial part. The North Sea: In the offshore stations, dissolved Hg concentrations are generally higher in winter than in summer while the reverse is true for particulate Hg K D values ( K D =the concentration of particulate Hg (Hg P in pmol kg −1 ) divided by the concentration of dissolved Hg (Hg D in pmol l −1 )) range from 100,000 to 1000,000 l kg −1 . Dissolved methylmercury concentrations vary from 0.05 to 0.25 pmol l −1 in summer and from d.l. to 0.23 pmol l −1 in winter and particulate methylmercury concentrations from 1.8 to 36 pmol g −1 in summer and from 0.9 to 21 pmol g −1 in winter. The K D ranges from 9,000 to 219,000 l kg −1 . The Scheldt estuary: In winter, dissolved Hg concentrations are elevated in the upper estuary, decrease exponentially in the low salinity range followed by a very slow decrease towards the mouth. In summer, they are low in the fluvial part, increase in the low salinity range or in the mid-estuary and sometimes show an increase in the lower estuary. Particulate Hg concentrations do not show any seasonal trend. Dissolved MMHg concentrations are much lower in winter, when maximum concentrations are found in the upper estuary, than in summer. In summer, the MMHg concentrations are low at low salinity, they show a first increase in the salinity range from 3 to 12, a decrease in the mid-estuary and a second increase in the lower estuary. The highest particulate MMHg concentrations are found in the upper estuary, while in the lower estuary generally lower and more constant values are observed. The ratio of dissolved MMHg to dissolved Hg (cruise averages between 1.3% and 20%), is higher than the ratio of particulate MMHg to particulate Hg (cruise averages of 0.27–0.90%). The K D values for MMHg are lower in the summer (30,000–65,000) than in autumn and winter (77,000–114,000). The Scheldt river: In the fluvial part of the Scheldt, dissolved increases in the most upstream stations, while particulate Hg shows no particular pattern. Dissolved MMHg ranges from 0.1 to 0.39 pmol l −1 and particulate MMHg from 3.1 to 43.5 pmol g −1 . The MMHg concentrations are comparable to those found in the estuary and no seasonal variations could be observed.

Elemental mercury concentrations and formation rates in the Scheldt estuary and the North Sea

Concentrations of Hg0 in surface waters and atmosphere of the Scheldt estuary and the North Sea are presented and their relationship with biological processes is discussed. Hg0 concentrations in the Scheldt estuary range from 0.1 to 0.38 pmol·l−1 in the winter and from 0.24 to 0.65 pmol·l−1 in the summer and show a positive relationship with phytoplankton pigments. In the North Sea Hg0 concentrations range from 0.06 to 0.8 pmol·l−1 and are higher in coastal stations. Transfer velocities across the air–sea interface were calculated using a classical shear turbulence model. Volatilization fluxes of Hg0 were calculated for the Scheldt estuary and the North Sea. For the Scheldt estuary the fluxes range from 226–284 pmol·m−2·d−1 in winter and 500–701 pmol·m−2·d−1 in summer and for the North Sea the fluxes range from 59–1110 pmol·m−2·d−1 for an average windspeed of 8.1 m·s−1. These fluxes are comparable to the wet and dry depositional fluxes to the North Sea. Hg0 formation rates necessary to balance the volatilization fluxes vary from 0.2 to 4% d−1.

Mercury speciation in hair by headspace injection-gas chromatography-atomic fluorescence spectrometry (methylmercury) and combustion-atomic absorption spectrometry (total Hg)

The speciation of Hg in human hair was carried out with combustion-atomic absorption spectrometry for total Hg (THg) and headspace-gas chromatography-atomic fluorescence spectrometry (HS-GC-AFS) for methylmercury (MMHg). The determination of total Hg in hair was carried out with the AMA analyzer (Advanced Mercury Analyser 254). Accuracy and reproducibility were assessed on a Certified Reference hair sample (IAEA-086 CRM), yielding, respectively, a recovery of 97.5% and a RSD of 3.2%. Analyses of 10 blank measurements resulted in a detection limit of 1.5 ng g(-1) of THg for a 20mg sample of human hair. MMHg concentrations in hair were assessed with HS-GC-AFS in a single analysis step. Either acid or alkaline extraction can be applied because they yielded very similar results on a IAEA-086 CRM: we observed a recovery of 103% and a RSD of 7% with acid extraction and a recovery of 110% and a RSD of 9% with alkaline extraction. Optimization of the headspace vial, injection and GC parameters is described. The detection limit of the MMHg determination in human hair, which amounts to 0.04 ng g(-1) for a 20mg sample, is far below the concentrations observed in natural samples. The number of samples that can be analyzed per hour, respectively, amounts to 8 for THg and 4 for MMHg. Finally, Hg speciation in natural human hair samples was carried out by combining both AMA and HS-GC-AFS analysis methods. THg levels were at the μg g(-1), level, with an average MMHg fraction of about 70%.

Determination of methylmercury in natural waters by headspace gas chromatography with microwave-induced plasma detection after preconcentration on a resin containing dithiocarbamate groups.

Abstract A method for the determination of methylmercury at ng l −1 levels in natural waters is described. Methylmercury present in a sample is first preconcentrated on a column of a resin containing dithiocarbamate groups and eluted quantitatively with acidic thiourea solution. Methylmercury in the effluent is then converted to the iodide by addition of sulphuric acid and iodoacetic acid and determined by headspace gas chromatography with microwave-induced plasma detection. The adsorption properties of the resin are discussed.

Early diagenetic processes aspects controlling the mobility of dissolved trace metals in three riverine sediment columns.

The behaviour of Mn, Fe, Co, Zn, Cd, Pb and Ni has been studied during early diagenesis in three different riverine sediments (Spierre, Lys and Sheldt). For that purpose (1) pore waters were extracted from sediment cores by centrifugation under nitrogen and further analyzed for the determination of total dissolved metal concentrations and (2) DET and DGT probes have been deployed in situ for the determination of high resolution profiles of labile and total dissolved metal concentrations. Furthermore, sulfidization processes have been examined; they revealed a production of pyrite near the water-sediment interface at Helkijn and Wervik sampling sites, probably due to a partial re-oxidation of reduced sulphur species. In Spierre sediments, where Eh values are the most negative, pyrite production should be mainly due to strict anaerobic processes. Concentrations of AVS in Spierre sediments are also very high and result in low TI values and low trace metal concentrations in the pore waters. Otherwise, in Wervik sediments, the low pH values combined to a TI value close to 0 results in the highest observed dissolved trace metal levels. DOS remains low at the three sites, since it does not exceed 0.4. In Wervik and Helkijn, the limitation is probably due to low sedimentary inputs of sulphate. In Spierre, sulphate is never exhausted in the pore water, suggesting a limitation of the DOS by a lack of bio-degradable organic matter. Values of Cd, Cu and Pb DGT concentrations remain low in pore waters whatever the site, due to their strong affinity with the reduced sulphur pool. It has also been demonstrated that the labile fractions of Pb and Cd are the lowest and do not exceed 0.5, while Co and Ni are the most available metals.

Storage and stability of inorganic and methylmercury solutions

SummaryThe storage behaviour of mercurychloride and methylmercury chloride solutions in deionized water and in seawater stored in polyethylene (PE), pyrex glass and teflon (PTFE) containers at various concentration levels (4 ppb, 50 ppt, natural seawater concentrations) was studied using various preservatives and container pretreament procedures. For PE bottles, the best results are obtained, after pretreatment of the bottles with an acidified KMnO4 solution, with a 0.05% (v/v) H2SO4+0.02% (w/v) KMnO4 preservative. However, the solution becomes heterogeneous rather fast, due to the formation of a MnO2 precipitate. Acidified (pH 1 with HNO3) deionized or seawater samples stored in pyrex glass BOD-bottles (analyses are carried out in these bottles too) or teflon containers are stable with respect to inorganic mercury for at least 1 month. Instead of acidification an oxidant such as BrCl can also be used to stabilize the solution. Methylmercury solutions (80 ppt) in deionized water (pH 6) and stored in teflon containers are stable for at least 1 month. In glass bottles, the solution should be acidified to pH 1. Methylmercury seems to be unstable in acidified seawater samples (pH 1 with HNO3); after 2 weeks about 60% of the methylmercury is converted into inorganic mercury.

Modelization of the mercury fluxes at the air-sea interface

Aqueous and atmospheric Hg° concentrations for remote marine areas such as the equatorial Pacific Ocean and for coastal seas such as the North Sea and the Scheldt Estuary are discussed. Biological processes seem to be at the origin of the supersaturated Hg° concentrations in the water. On the other hand, transfer velocities across the air-sea interface were calculated with a classical shear turbulence model and with a wave breaking model. With these data, Hg° fluxes from the sea to the atmosphere were calculated: in the Pacific Ocean they range from 0.43 to 6.5 μg g Hg.m−2. yr−1 at a wind speed of 2.8 m.s−1 and from 10.3 to 156 μg Hg.m−2 yr−1 at a wind speed of 54 m.s−1, but they are still higher when wave breaking is considered (from 11 to 168 μg Hg.m−2.yr−1). These transfer fluxes are an order of magnitude higher in the Scheldt Estuary.

Dietary exposure to total and toxic arsenic in Belgium: Importance of arsenic speciation in North Sea fish

Total and toxic (sum of As(III), As(V), monomethylarsenic (MMA), and dimethylarsenic (DMA)) As concentrations were assessed in 19 respectively 4 different fish and shellfish species from the North Sea. Following results were obtained: (i) for fish an average total As concentration of 12.8 microg/g ww and a P90 value of 30.6 microg/g ww; (ii) for shellfish an average total As concentration of 21.6 microg/g ww and a P90 value of 40.0 microg/g ww; (iii) for fish an average toxic As concentration of 0.132 microg/g ww and a P90 value of 0.232 microg/g ww; (iv) for shellfish an average toxic As concentration of 0.198 microg/g ww and a P90 value of 0.263 microg/g ww. For the Belgian consumer the average daily intake of total arsenic from fish, shellfish, fruit, and soft drinks (the main food carriers of As in Belgium) amounts to 285 microg/day with more than 95% coming from fish and shellfish, while for a high level consumer it amounts to 649 microg/day, more than twice the average value. Using the same daily consumption pattern for the selected food products as for total As, we find that the average daily intake of toxic As amounts to 5.8 microg/day, with a 50% contribution of fish and shellfish and the high level intake to 9.5 microg/day. When considering the FOA/WHO Expert Committees recommendation for inorganic As intake of 2 microg/kg bw/day or 140 microg/day for a 70 kg person, the toxic dose in Belgium is thus an order of magnitude lower.

Sources of PCDD/Fs, non-ortho PCBs and PAHs in sediments of high and low impacted transboundary rivers (Belgium–France)

PAHs, PCDD/Fs and non-ortho PCBs have been assessed in Yser and Upper-Scheldt river sediments. Higher contamination levels were observed in the Upper-Scheldt sediments: maximum concentrations for the 16 US-EPA PAHs, PCDD/Fs and non-ortho PCBs respectively amount to 8.9 mg kg(-1), 12 ng TEQ kg(-1) and 5.1 ng TEQ kg(-1). Diagnostic PAH ratios in sediments and atmospheric samples suggest that the PAH compounds are from pyrolytic origin, more specifically combustion processes. The huge consumption of coal in cokes-ovens and smelters and its use for house-heating in Northern France, although decreasing during the last decades, are in support of that suggestion. PCDD/F fingerprints in sediments and deposition material indicate that OCDD is the dominant congener. In addition use of pentachlorophenol (PCP) in the past led to a minor contribution of PCDD/Fs in our sediment samples. Non-ortho PCBs form a substantial fraction of the total TEQ concentrations observed in the sediments. Since the 1980s and 1990s a substantial reduction of the PCDD/F sediment concentrations is observed, but this is not the case for the PAHs.